A furore in Saudi Arabia over alleged apostasy in a Twitter post threatens the lively internet culture that invigorated Saudi discourse in recent years, warns a media expert.

Hamza Kashgari, a writer and newspaper columnist, made a series of postings on Twitter late last week, around the date that Muslims celebrate the Prophet's birth, in which he discussed the Prophet Mohamed.

The postings were interpreted by many to be an insult to religion. He later deleted the posts, closed his account and issued an online apology.

But the response – tens of thousands of furious tweets, many calling for his trial and execution – led him to flee the kingdom, where charges of apostasy can lead to long jail terms or the death penalty.

Saud Kateb, a professor of new media at King Abdelaziz University, said that while the comments were unacceptable according to Saudi norms, the response, including violent threats and offers of rewards to those who kill Mr Kashgari, merited a firm reaction from the authorities.

"We don't accept anyone insulting our God and our Prophet, but to threaten other people's lives is unacceptable, and the government must take action about this," he said.